In the pet food industry, palatability enhancing materials, often referred to as “palatants,” may be provided to certain foods categorized generally as “kibble,” to increase enjoyment of the food while providing for the nutritional needs of the animal. As used in this industry, “palatability” generally encompasses within its meaning all of the various properties of the food that can be sensed by an animal, including taste and smell. Materials such as animal origin digests, organic acids and their salts, and different types of meat proteins are commonly used to enhance the palatability of the pet foods. These may be either liquid or dry, depending on the desired properties. It is also desirable to increase other properties of the animal food while maintaining its palatability. Therefore, functional additives, such as probiotic microorganisms, vitamins, certain pharmaceutical compounds, and tartar control agents, may be provided in animal food to increase the overall benefit to the animal. Palatants and other functional additives can either be incorporated into the food or can be topically applied onto the surface of the food. Surface application is commonly done following extrusion of the food product. Surface application is generally preferred as a method of providing these additives, because either the flavor of the additive, such as a palatant, can be masked by other ingredients within the kibble, or the additives may lose their desired properties through process-sensitive decomposition if they are incorporated into (i.e., intermixed with) the food composition itself. Further more, it is known that some additives, such as tartar control agents, may be made more immediately available at a higher concentration in the oral cavity if provided on the surface of the animal food. It is therefore often preferred in the art to surface coat the animal food with the palatants and other beneficial additives.
In general, application of materials to the surface of the food is usually performed using a staged application or other types of processes. With respect to the staged surface coating process, it is common in the art to apply liquid fat to the surface of the animal food, followed by the application of dry and liquid additives. In the staged application process, the liquid fat is generally used as a binder to secure the dry and liquid additives to the surface of the animal food. To utilize the fat as a binder in staged application, however, dry and liquid additives generally must be applied in excess to ensure that the animal food is sufficiently coated with the additives, and a significant amount of the excess additives may be wasted, thereby contributing to increased costs of production, raw material, storage, and clean-up. Furthermore, it may be difficult to optimize or change the amounts of dry and liquid additives applied to the surface of the animal food when changing from one product to another without having to first shut down the entire staged application process. When changing the mixes for different product runs, entire batches of liquid-dry mixes must be removed and exchanged.
To overcome some of the problems associated with the staged application process, a simultaneous application process is often employed as alternative. In the simultaneous application process, liquid fat is used as a carrier and binder substrate for the dry and liquid additives. Specifically, liquid fat, dry additives, and liquid additives are mixed simultaneously to form a surface coating composition. Other approaches result in highly viscous compositions, which can be more difficult to provide the ingredients to the surface of the food in a uniform manner. Furthermore, many of the dry materials contained in the surface coating composition, such as, for example, vitamins, antioxidants, probiotic microorganisms, pharmaceuticals, enzymes, peptides, proteins, herbals, flavors, and the like, may more likely be degraded during mixing when all additives are combined well before application, thereby increasing the exposure of certain ingredients to process and environmental conditions such as moisture, acidic components within a prepared digest, heat, shear or pressure, or a combination of two or more of these or other deleterious factors. Specifically, the liquid additives, which are likely aqueous and highly acidic, may subject dry additives to hygroscopic effects such pH change or water activity due to exposure to water during mixing, causing a loss of desired efficacy of the dry additives.
Therefore, there exists a need in the art for a process of surface coating animal food with dry and liquid additives that overcomes the aforementioned problems.